From: Damien Broderick (d.broderick@english.unimelb.edu.au)
Date: Tue Oct 01 2002 - 21:29:26 MDT
At 10:26 AM 10/1/02 -0400, Rafal wrote:
>>Maybe it's like the lottery:
>> everyone in town has a chance of winning, and once you win you leave
>> the god-forsaken hole and head for the beach. This doesn't make it
>> harder for succeeding generations to win the lottery.
>### Actually, whenever a smart person leaves town, he/she takes the smart
>genes away.
This of course is precisely the model I'm questioning.
>If you conceptualize mating with a smart person to produce smart
>offspring as winning a lottery, then these genes are the winning tickets.
>The not-so-smarts remaining in town are left playing a lottery with fewer
>and fewer winning tickets.
Suppose the genetic component of IQ is a vector of the 10-15,000 genes and
their alleles that apparently govern the brain's architecture and its
operations. There will be disorders and deficits due to mutations that
badly damage some of those genes, but most of those seem also to lead to
sterility. Now it's clear that families like the Huxleys and the Darwins
produce a much larger proportion of high IQ offspringen than JoeBob Gulch's
kids; modulo enriched vs. impoverished intellectual/cultural/nutritional
environment, I'd guess that these hypersmart families are indeed passing
along some closely linked genes that conduce to high IQ performance. But
regression to the mean arguments imply that such massively polygenic traits
as IQ keep getting remixed almost stochastically. IQ range between sibs in
a largish family seems to vary by 30 points or more.
Consider: if there is a small number of `smartness genes', by now moieties
of humans would have separated into IQ `breeds' as distinctive as Lee
Corbin's puppydog breeds. I don't know how the mixing process works, but
Hans Eysenck, not known for his far-left views, was where I learned about
`regression to the mean' in IQ. As far as I can see, the correlation of
child and parent doesn't work to make ever brainer and ever stupider kids
in each generation via assortative mating; if that had happened, you
wouldn't just see the Flynn effect, you'd be living in a culture where the
top IQ had risen by a point a generation (or whatever) for the last 10,000
years at least. But maybe the effect saturates.
Damien Broderick
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